Microstructure and mechanic properties of SiC reinforced cobalt-based alloy coatings deposited by plasma transferred arc welding

SiC reinforced cobalt-based alloy composite coatings on the surface of the low carbon steel substrate was deposited by plasma transferred arc (PTA) weld surfacing by using synchronization powder feeding method. The mass fraction of SiC was 5%, 10% and 20% respectively. Microstructure and phase composition were characterized by optical microscope, scanning electron microscopy (SEM), X-ray diffraction and energy dispersion spectroscopy. The Vickers microhardness and elasticity modulus were tested by microhardness tester and nano-indenter, respectively. Results indicated that γ-Co and Cr₂₃C₆ existed in the cobalt-based alloy coatings. The phases of (C, Fe)r₇C₃, CoC_x, Co₃C and a small amout of SiC appeared with addition of different content of SiC ceramic particles. Hypoeutectic microstructure was observed in Co-based alloy coatings, which changed to eutectic and hypereutectic form with increase addition of SiC. The microhardness was improved with increase of SiC addition, and it reached HV0.5874 with 20% SiC. The nanoindentation tests indicated that hardness of the solid solution and the elastic modulus near the fusion line increased with increase of SiC addition.